1. Field of the Invention
The present invention generally relates to the field of vehicle lifts which enable persons who are physically challenged or otherwise have limited mobility to board and leave a bus or a vehicle. More particularly, the present invention relates to the field of vehicle lifts which have improved driving mechanisms for moving a platform between retracted (stowed) and extended (deployed) positions.
2. Description of the Prior Art
Vehicle lifts are widely used for enabling persons who are physically challenged or otherwise have limited mobility to board and leave vehicles, such as a bus. Generally, considerations relative to an effective vehicle lift have included safety, ease of use, economy, space requirements and durability. Although a variety of mechanisms and structures have been introduced, a need has continued for an improved lift to transport persons who are physically challenged or otherwise have limited mobility to board and leave the vehicle.
One of the prior art vehicle lifts includes a platform carriage, horizontally movable between a stowed position within a vehicle and a deployed position outboard of the vehicle. The platform carriage is typically extended or retracted by a driving mechanism which may be on both sides of the platform carriage and arranged in a vertical plane arrangement. A platform located in the carriage is mounted to swing in an arcuate path for lifting and lowering physically challenged persons between ground level and the floor level of the vehicle.
U.S. Pat. No. 4,058,228 issued to Hall on Nov. 15, 1997 discloses a passenger vehicle access stair and elevator apparatus. The platform extends and retracts by a conventional prior art drive mechanism which includes a chain and sprocket drive means mounted in a vertical plane arrangement.
U.S. Pat. No. 4,134,504 issued to Salas et al. on Jan. 16, 1979 discloses a lift for a wheelchair. The platform extends and retracts by a cable drive means which is mounted in a vertical plane arrangement.
U.S. Pat. No. 4,909,700 issued to Fontecchio et al. on Mar. 20, 1990 discloses a lift for a wheelchair. It comprises stationary track members which are attached to a vehicle, and frame members slidably mounted within the track members, where the frame members extend or retract from the vehicle by use of a pair of worm gears. A pair of hydraulic cylinders interconnect the platform and the frame members using four links which raise and lower the platform. The worm gears are mounted in a vertical plane arrangement.
U.S. Pat. No. 4,958,979 issued to Svensson on Sep. 25, 1990 discloses an arrangement for a lift adapted to a motor vehicle. It comprises a lifting platform capable of moving between the vehicle and a floor. The lifting platform is attached by a scissors mechanism to a source of power for the platform, so that the platform, upon actuation of the power source, moves between a lower and an upper position.
U.S. Pat. No. 5,111,912 issued to Kempf on May 12, 1992 discloses a spring loaded drive assembly for a wheelchair lift. The drive assembly includes a set of linkage arms connected between the platform and a stable carriage arm. A pair of sprockets are connected to the carriage arm at the linkage arm pivot points and control the rotation of the linkage arms and the movement of the platform relative to the carriage arm. The sprockets are connected together by a leaf chain assembly so as to slow rotation of sprockets in a simultaneous movement of the arms. The drive assembly is mounted in a vertical plane arrangement.
One of the inventors and a co-applicant of the present invention is also the patentee of U.S. Pat. No. 5,253,973 issued on Oct. 19, 1993 for "Vehicles And Vehicle Lifts" (hereafter the "'973 Patent") and U.S. Pat. No. 5,556,250 issued on Sep. 17, 1996 for "Vehicle Lifts" (hereafter the "'250 Patent"). While the patentee's prior art vehicle lifts function adequately, the patentee has continuously sought to further improve his products for persons who are physical challenged or otherwise have limited mobility to board and leave a vehicle.
The '973 Patent discloses a lift for attachment to a vehicle for moving mobility-impaired passengers between lowered and raised positions for entry and exit. A platform is affixed to an unequal modified parallelogram structure and supported on movable rails and is carried by rollers for movement between extended and retracted positions by a driving assembly. The driving assembly is mounted in a vertical plane arrangement.
The '250 Patent discloses a vehicle lift which comprises a drive mechanism which is mounted in a vertical plane arrangement.
Prior art lifts as described above have been useful and effective, however, as indicated, the need for improvement has continued. It is highly desirable to provide a very efficient and also effective design and construction of a horizontally movable mechanism that is capable of smooth motion without binding or catching between the stowage and deployed positions. It is desirable to provide an improved driving mechanism mounted in a horizontal plane arrangement which is more compact than the existing vertical arrangement. It is also desirable to provide an improved driving mechanism to be able to move the lift platform either electrically or manually between the stow position and the deployed position. In addition, it is desirable to provide an effective alignment of the platform for stowage.